Our working hypothesis is that tumor transformation in higher plants, and perhaps generally, is due to epigenetic changes rather than permanent alterations in the cell genome. The main objective of the proposed work is to find molecular mechanisms for epigenetic changes that perpetuate growth autonomy in crown-gall, a neoplastic disease of higher plants. Specifically, we plan to test the hypothesis that cytokinin autotrophy, a key feature of plant tumor cells, is maintained by a positive feedback loop in which cytokinins induce the autotrophic state. BIBLIOGRAPHIC REFERENCES: Meins, F., Jr. (1976), 5 Bromodeoxyuridine: A specific inhibition of cytokinin-habituation in tobacco cell culture. Plants 129, 239-244. Pengelly, W. and Meins, F., Jr. (1976), A radioimmunoassay for indole-3-acetic acid. Plant Physiol. 57 suppl., 30.